The present invention relates to novel diphosphonic acids and diphosphonic acid esters of para-menthane and to their production.
Kenney and Fisher report in J. Org. Chem., Vol. 39, No. 5, pages 682-686 (1974) that the reaction of .beta.-pinene with diethyl hydrogen phosphite in the presence of di-tertiary-butyl peroxide yields a monophosphonate (diethyl-para-menth-1-en-7-ylphosphonate). Under the same reaction conditions using .alpha.-pinene, a monophosphonate also was formed (diethyl-para-menth-1-en-6-ylphosphonate). Similarly, Francois and Lalande report in C. R. Acad. Sci., Ser. C., Vol. 279, No. 3, pages 117-119 (1974), that these same monophosphonate products can be made using benzoyl peroxide and di-tertiary-butyl peroxide to catalyze the reaction.
The present invention discloses the novel diphosphonic acids and diphosphonic acid esters of para-menthane. These products are potentially useful as flame retardants and are useful as treating agents for improving the pigmentary properties of pigmentary titanium dioxide in thermoplastic formulations.